The present invention relates to an electroacoustic transducer for a speaker configured to reproduce sounds by vibrating longitudinal split tubular surfaces and to a microphone configured to pick up sounds.
In conventional cone-type speakers, an end portion of a voice coil as a driving device and an end portion of a cone-type membrane are joined to each other in their entire perimeter, enabling good transmission of vibration. However, in the case where sounds over a wide audible frequency range are reproduced by a single speaker unit, directivity is not uniform between a high frequency range and a low frequency range, resulting in narrow directivity over the high frequency range. To make the directivity uniform over all the audible frequency ranges, a speaker specific to the high frequency range is required.
As disclosed in Japanese Patent No. 3521319 for example, riffell speakers in contrast include a diaphragm having a pair of longitudinal split tubular membranes arranged side by side, and side portions of the respective longitudinal split tubular membranes are joined to each other, resulting in good directivity at the middle and high frequencies. In such a riffell speaker, however, since the coupled portion of the membranes extends straight, the coupled portion of the membranes and a circular voice coil are coupled to each other at only two positions, resulting in a weak construction. Thus, the coupled portions have low durability, and transmission of vibration is not reliable. Moreover, Japanese examined Patent Application Publication No. 32-7807, for example, discloses a speaker having V-shaped cuts in end portions of a voice coil. A bent portion of a wing-pair membrane is mounted in these cuts. In this speaker, mounting the membrane in the cuts formed in the voice coil increases the strength of the coupled portions when compared with the speaker disclosed in Japanese Patent No. 3521319. However, this increase is not sufficient, and further improvement is required.